A calculation device for deriving solutions of a system of linear equations, which realizes a solution of the system of linear equations using an iterative method belonging to a Krylov subspace method, includes a plurality of arithmetic units. In the calculation device, a vector sequence xk (k is a natural number containing 0) approximating to the solutions of the system of linear equations is formed by a plurality of components in accordance with an order of the vector sequence xk, and when the vector sequence xk is divided into a plurality of different regions corresponding to the plurality of components and the respective arithmetic units are caused to execute arithmetic processings corresponding to the plurality of different regions in parallel in iterative computation of causing the vector sequence xk to approximate to the solutions, a preconditioned matrix that is used in the iterative computation is a diagonal matrix.